Different unidirectional and bidirectional systems for transmitting data between base stations and nodes are known, such as DECT (DECT=Digital Enhanced Cordless Telecommunications) and RFID (RFID=Radio-Frequency Identification). It is typical for these systems that the base station specifies a reference frequency and a reference time with which the participants synchronize. In RFID systems, for example, the reader specifies a time window following immediately after its emission, within which the RFID transponders arbitrary select a time for the response. The specified time interval is additionally divided into timeslots of equal length. This is called a slotted aloha protocol. In DECT, however, time slots are provided within a fixed grid. Here, the base station allocates an exact timeslot to a participant that he may use for communication. Due to the inaccuracy by the quartz tolerance, a buffer time is provided between the timeslots so that the telegrams do not overlap.
DE 10 2011 082 098 B4 describes a battery-operated stationary transmitter arrangement and a method for transmitting a sensor data packet where the sensor data packet is divided into several data packets that are smaller than the actual information that is to be transmitted (telegram splitting). Here, telegrams are divided into several partial packets. Such a partial packet is referred to as hop. In one hop, several information symbols are transmitted. The hops are transmitted on one frequency or distributed across several frequencies (frequency hopping). In between the hops are breaks where no transmission takes place.
Since not only the transmission of data but also the reception of the same entails comparatively high energy consumption, the same system can also be used for the reverse case where data are transmitted from the base station to the node. In this scenario, the energy consumption of the nodes is also to be kept low since the nodes possibly have no constant current supply but practice energy harvesting where the nodes draw energy from the environment (e.g. temperature differences, sunlight, electromagnetic waves etc.) or, as in DE 10 2011 082 098 B4 for transmitting, a battery is available accordingly for receiving which cannot provide the current for the receiver over a sufficiently long time period.
Apart from energy consumption, costs are also a significant criterion when designing a receiving node. Due to that, mostly very simple radio chips (receiver or transceiver) that have low acquisition costs and can operate in an energy-efficient manner can be found on these nodes. However, due to their simple structure, these radio chips lack the ability of determining detailed information on the quality of the channel or the received data. Also, such radio chips offer no option of providing the information necessitated for calculation to another chip. Additionally, the exact channel analysis in an external controller would also cause significant energy consumption. Normally, these cost-effective receiver chips provide an already demodulated digital bit sequence at their output (=decided bits).